Melophorus hirsutus Forel

Heterick, Brian E., Castalanelli, Mark & Shattuck, Steve O., 2017, Revision of the ant genus Melophorus (Hymenoptera, Formicidae), ZooKeys 700, pp. 1-420 : 330-332

Melophorus hirsutus Forel

Melophorus hirsutus Forel 1902: 488 (combination in M. (Trichomelophorus) by Wheeler 1935: 71).

Types. Syntype major and minor worker: MacKey, Queensland [MHNG] (examined: MHNG specimens).

Other material examined.

Australian Capital Territory: ANU (CFS) (Narendra, A. [M167]), Black Mountain (Taylor, R.W. [ANIC32-900043]), Black Mountain Reserve (Devonshire, J. [ANIC32-045115]), Black Mt., Site 1 (Barnett, N.J. [ANIC32-029779]), Mt. Ainslie (Shattuck, S.O. [ANIC32-047357]). New South Wales: 10 mi N Berowra (Lowery, B.B. [ANIC32-900035]), 4 km NE Mt. Wog Wog, 17 km SE Bombala (Margules, C.R. [ANIC32-900045]), 8 mi W Somerton (Greaves, T. [ANIC32-900038]), Armidale (Lowery, B.B. [ANIC32-900046]), Belanglo State Forest (Gush, T. [ANIC32-900034]), Bilpin, Blue Mountains (Lowery, B.B. [ANIC32-900032]), Burns Bay on Lane Cove River, Sydney (Lowery, B.B. [ANIC32-900044]), Eulah Creek, Narrabri (Room, P. M. [ANIC32-900040]), Katoomba (Wheeler, W. M. [ANIC32-900033]), Ourimbah State Forest (Lowery, B.B. [ANIC32-900039]), Uralla (Wheeler, W. M. [ANIC32-900049]), Whiporie, 55 km S Casino (York, A. [ANIC32-900041]). Queensland: Buhot Ck, Burbank (QM Party), Cairns (general) (Greaves, T. [ANIC32-045325]), Camp Mountain, Brisbane (Lowery, B.B. [ANIC32-900037]), Camp Mountain, Brisbane (Lowery, B.B. [ANIC32-900048]), Kirrama (Crowley, G. [ANIC32-900047]), Lords Table, SE base (Burwell), Peawaddy Gorge Lkt, 1 km S (Eddie, C. et al.), Tindaree, Hannaford Rd South via Tara (House, A./Brown, S.). Victoria: Ferntree Gully (Greaves, T. [ANIC32-900031]), Greensborough (McAreavey, J. [ANIC32-900036]), Lerderderg Gorge (Lowery, B.B. [ANIC32-900042]).

Diagnosis.

Melophorus hirsutus is distinguished from all other Melophorus by having the pronotum surrounded by a translucent lamina, the metanotal groove obsolete in the minor worker and just a weak furrow in major worke, the torulus pedunculate around the antennal insertions, and the cuticle of mesosoma with dense striolate-microreticulate sculpture. The ant is monotypic for its species-complex, but is tentatively placed in the M. ludius species-group on the basis of molecular evidence. The species is restricted to the eastern Australian seaboard.

Minor worker description.

Head. Head approximately oval with straight sides; posterior margin of head weakly convex; frons shining and smooth except for piliferous pits and a few striolae around antennal insertions and frontal carinae; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye small (eye length less than 0.2 × length of side of head capsule); in full-face view, eyes set at about midpoint of head capsule; in profile, eye set around midline of head capsule; roughly ovoid, eye narrowed posteriad. In full-face view, frontal carinae absent or weakly produced in front of antennal insertions; frontal lobes pedunculate. Anteromedial clypeal margin broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five to six mandibular teeth in minor worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately vertical or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining and striolate-micropunctate, with some shallow, oval depressions; anterior mesosoma in profile smoothly rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on same plane as propodeum; appearance of erect pronotal setae long (i.e., longest erect setae longer than length of eye) and unmodified; in profile, metanotal groove vestigial but indicated by metathoracic spiracles; propodeum shining and finely striolate and microreticulate; propodeum planar dorsally with abrupt declivity; length ratio of propodeal dorsum to its declivity about 1:1; erect propodeal setae present and abundant (greater than 12); appressed propodeal setulae sparse or absent, if present then not regularly spaced; propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length <0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node uniformly rounded; node shining and smooth throughout. Gaster. Gaster smooth and glossy; pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with regularly placed appressed setae. General Characters. Colour dark reddish brown, appendages tan.

Major worker description.

Head. Head square; posterior margin of head planar or weakly concave; cuticle of frons shining and finely striolate and microreticulate; pilosity of frons a mixture of a few well-spaced, erect setae interspersed with appressed setae only. Eye small (eye length less than 0.2 × length of head capsule); in full-face view, eyes set at about midpoint of head capsule; in profile, eye set anteriad of midline of head capsule; eyes elliptical. In full-face view, frontal carinae absent or weakly produced posteriad of antennal insertions; frontal lobes pedunculate. Anterior clypeal margin broadly and evenly convex; clypeal psammophore set at or just above anterior clypeal margin; palp formula 6,4. Five mandibular teeth in major worker; mandibles triangular, weakly incurved; third mandibular tooth distinctly shorter than apical tooth and teeth numbers two and four; masticatory margin of mandibles approximately aligned vertically or weakly oblique. Mesosoma. Integument of pronotum, mesonotum and mesopleuron shining and striolate-micropunctate, with some shallow, oval depressions; anterior mesosoma in profile smoothly rounded anteriad, thereafter pronotum and whole of mesonotum flattened and on same plane as propodeum; erect pronotal setae long (i.e., longer than length of eye) and unmodified; in profile, metanotal groove shallow, indicated mainly by an angle and metathoracic spiracles; propodeum shining and finely striolate and microreticulate; propodeum planar dorsally with abrupt declivity; length ratio of propodeal dorsum to its declivity between 1:1 and1:2; erect propodeal setae present and abundant (at least a dozen); appressed propodeal setae sparse or absent, if present then not regularly spaced propodeal spiracle situated on or beside declivitous face of propodeum, and shorter (length less than 0.50 × height of propodeum). Petiole. In profile, petiolar node squamiform; in full-face view, shape of petiolar node generally rounded with median indentation, node shining and smooth throughout. Gaster. Gaster smooth and glossy; pilosity of first gastral tergite consist ing of a mixture of curved, erect and semi- erect setae and decumbent setae that form a variable pubescence. General characters. Colour of head crimson, mesosoma dark reddish-brown, gaster brown, appendages dark tan.

Measurements.

Worker (n = 6): CI 106-119; EI 12-17; EL 0.15-0.19; HL 0.82-1.26; HW 0.87-1.51; ML 1.18-1.75; MTL 0.75-1.07; PpH 0.13-0.18; PpL 0.62-0.73; SI 91-124; SL 1.37-1.08.

Comments.

Along with M. majeri this peculiar species is the most morphologically aberrant Melophorus , with its barrel-like mesosoma (not unlike that of some diapriid wasps), a variably pedunculated torulus otherwise found only in some M. mjobergi complex species and in one population of M. lanuginosus , and the margins of the pronotal humeri that are flattened to form a translucent flange. The range of this species is also unusual, as its main distribution is in the mountains and hills of the Great Dividing Range south of about Brisbane. North of Brisbane, although there are a few scattered records along the Great Dividing Range as far north as Cairns. States in which this ant occurs include ACT, NSW, QLD and Vic. There are no records for the NT, SA, Tas or WA.

The syntype major and minor workers reveal a rather conservative appearance compared with some populations: the torulus is only weakly pedunculate, the metathoracic spiracles are narrowly protuberant but not stalk-like and the compound eyes are of normal appearance. The two MHNG specimens appearing on separate points on the same pin are accompanied by one of Forel’s red ‘typus’ labels and almost certainly represent the two workers to which he refers in his description. The supposed syntype specimen Automontaged by AntWeb as CASENT0903268 (BMNH) should therefore be removed from the type series, despite similar collection details.

The morphology of the ant is very variable, the conformation of the eye being particularly noticeable and this may be of taxonomic significance: in some specimens the eye is quite conical and bizarrely projecting, while in others it is merely slightly bulbous. Intermediate states have been seen. Identifying and finding a pattern in this morphological variability would make for a worthwhile student project. Unfortunately, sequenceable material has been too limited in this project to be of use in identifying such variation, with only one specimen providing a signal for the five genes used in this project. Although tentatively placed within its own complex because of its odd morphology, mtDNA situates this species more broadly within the M. ludius species-group. However, this species shares with the M. biroi species-group the extremely flattened petiolar node in the major worker. Specimens have been collected in a variety of woodland habitats, including remnant brigalow, eucalypt forest and riparian forest.